PID Cherenkov Session at CM 20/1

Jochen Schwiening, GSI Darmstadt, "Barrel DIRC status"

The first batch of radiator bars have arrived from Nikon Corp., Japan. and
quality assurance by the Barrel DIRC group has started. Nikon QA data looks
very good, all specs are met or exceeded.
The status of the MCP-PMT tendering is in an advanced stage: initial offers
from 3 companies were received, negotiations with two vendors are still ongoing.
There are concerns about technical qualification of one of the vendors, therefore,
two sample units from both vendors in Nov 2019 were ordered.
Two evaluation tubes from the first vendor were received in late January,
tubes from the second vendor are expected in April.

Simon Bodenschatz, Uni Giessen, "Giessen Cosmic Station - Status Update"

Simon showed the setup and the expected performance based on simulation results.
The goal is to test the radiator plate and the readout with cosmics.
In parallel, Cherenkov measurements with SiPM array and an aerogel radiator will be done.

Steffen Kraus, FAU Erlangen, "First results of the Photek A1200107 & A3191220 2x2 inch² MCP-PMTs"

The quantum efficiency and the gain of the two MCP-PMTs from Photek were measured.
Both tubes have QE larger than 20% and a gain of 10e6. The gains at the edges of
the tubes is 5-10 times smaller. The rate stability exceeds 600 kHz/cm2 which are
the requirements for the Barrel DIRC. Also the timing precision, the darc count rate,
the after pulse probability, the cross talk between channels were measured.

Merlin Boehm, FAU Erlangen, "TRB/DiRICH measurements and the ToT structure"

The time over threshold shows for small MCP-PMT signals a bumpy distribution with unclear origin
when measured with the PADIWA-TRB3 or the DiRICH DAQ systems.
By waveform measurements with the scope, Merlin excluded the DAQ system as reason. He thinks that
back-scattered photoelectrons/electrons broadens the signals. He plans tests with different voltages
between photocathode and MCP.